Wellhead completion assembly capable of versatile arrangements

ABSTRACT

A wellhead completion assembly has a head connected to surface casing. A rotatable flange or the like can be used to connect various components to a threaded end of the head. A casing hanger installs in the head, and the hanger&#39;s upper end extends beyond the head&#39;s top edge. This exposed end has an external threaded connection to connect to various wellhead components using a rotatable flange or the like. For example, a locking ring can threadably connect to the head&#39;s threaded end to support the hanger in the head. Then, a rotatable flange can threadably connect to the hanger&#39;s exposed end so that another component, such as a completion spool or gate valve, can nippled up directly to the hanger. When the hanger is fluted, a pack-off assembly can allow testing off inner and outer sealing integrity via a test port accessible through an opening in the locking ring.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. application Ser. No. 11/925,498, filed 26Oct. 2007, which is incorporated herein by reference and to whichpriority is claimed.

BACKGROUND

A well has one or more casings installed in a borehole to reinforce andseal it, and wellhead components install at the surface above theexposed end of the casings. For example, FIG. 1 shows a wellheadarrangement according to the prior art. Typically, an outermostconductor pipe is driven into place in the borehole, and a base assembly11 is on the exposed end of conductor pipe 10. A casing head 30 lands onthe base assembly 11 and connects to a surface casing 14 supportedinside the conductor pipe 10. Typically, the space between the casing 14and pipe 10 is filled with cement. One or more adapters 40 andcomponents 50 of a blow-out preventer can connect above the casing head30. As shown in FIG. 1, flanged connections are typically used toconnect the various components together.

Because various operations may be performed at the wellhead, thearrangement of components may be modified to accommodate differentoperations, pressures, and implementations. One typical wellheadoperation involves fracing. According to conventional practices, anisolation tool, such as a stinger, installs in the wellhead to isolatebores and outlets from pressures that may be higher thanpressure-ratings for the wellhead's flange connections.

In one typical wellhead arrangement, a casing hanger supports casing inthe casing head, and a tubing spool nipples to the casing head so thatanother hanger can be used in the tubing spool to support tubing in thecasing. Typically, an adapter must be installed on the casing head priorto nippling up the tubing spool so that the adapter can pack-off or sealaround the casing hanger. In another typical wellhead arrangement, afluted casing hanger support casing in the casing head so that drillingfluids during cementing operations are allowed to return through thehanger's flutes. Later, a pack-off bushing installs above the flutedcasing hanger to seal off the flutes. Typically, there is only a limitedability to test the seal created by such a pack-off.

SUMMARY

A wellhead completion assembly is capable of versatile arrangements. Theassembly has a first head component that connects to surface casing. Arotatable flange or the like can be used to connect various componentsto a threaded end of this first head component. Alternatively, secondhead components can threadably stack on top of one another and canthreadably stack on top of the first head component to create amulti-bowl arrangement.

For either arrangement, the assembly can use a casing hanger thatinstalls in the head (i.e., first head component in a single-bowlarrangement or the top most second head component in a multi-bowlarrangement). In either case, the hanger's upper end extends beyond thehead's top edge. This exposed end has an external threaded connection toconnect to various wellhead components using a rotatable flange or thelike. For example, a head or locking ring can threadably connect to thehead's threaded end to support the casing hanger in the head. Then, arotatable flange can threadably connect to the hanger's exposed end sothat another component, such as a completion spool or gate valve, cannippled up directly to the casing hanger.

The casing hanger can be fluted or not, and a pack-off plate can be usedto seal the casing hanger in the head. This pack-off plate can have atest port accessible through an opening in the head ring holding thehanger in the head. The test port allows operators to test the inner andouter sealing integrity of the pack-off plate. In one particulararrangement, the casing hanger has a sealing ring positioned about itsexternal surface. The pack-off plate threads onto an external threadedconnection on the casing hanger, and a lip on the pack-off platepositions in wedged engagement between the sealing ring and a portion ofthe external surface of the casing hanger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view illustrating a wellheadarrangement according to the prior art.

FIG. 2 is a cross-sectional view illustrating a wellhead completionassembly in one arrangement having portion of a Blow-Out Preventer (BOP)stack nippled up to a casing head.

FIG. 3A is a cross-sectional view illustrating the assembly of FIG. 2 inanother arrangement having a completion spool nippled up to the casinghanger.

FIG. 3B is a detail illustrating portions of the casing hanger, thelocking ring, and the casing head of FIG. 3A.

FIG. 4 is a cross-sectional view illustrating the assembly of FIG. 2 inyet another arrangement having a gate valve nippled up to the casinghanger.

FIGS. 5A-5B are top and cross-sectional views illustrating a flutedcasing hanger for the disclosed assembly.

FIG. 6 is a cross-sectional view illustrating a pack-off plate.

FIG. 7A is a partial cross-sectional view illustrating a flange and thepack-off components on the fluted casing hanger of FIGS. 5A-5B.

FIG. 7B is a detail of FIG. 7A illustrating features of the pack-offcomponents.

FIG. 8 is a cross-sectional view illustrating the casing head of FIG. 2landed through a riser.

FIGS. 9A-9B are cross-sectional views illustrating the casing head ofFIG. 2 used with other wellhead components.

FIG. 10A is a cross-sectional view illustrating another embodiment of awellhead completion assembly in one arrangement.

FIG. 10B is a cross-sectional view illustrating the assembly of FIG. 10Ain another arrangement.

FIGS. 11A-11E are cross-sectional views illustrating a wellheadcompletion assembly having modular head components in various stages ofassembly,

FIGS. 12A-12B are cross-sectional views illustrating the modularassembly using only a first head component.

FIG. 13 is a cross-sectional view illustrating the modular assemblyusing three head components.

FIGS. 14A-14C are cross-sectional views illustrating the modularassembly when stuck pipe occurs.

FIGS. 15A-15C are cross-sectional views illustrating the modularassembly having a control line when stuck pipe occurs.

DETAILED DESCRIPTION

A versatile wellhead completion assembly is capable of variousarrangements. The assembly includes a casing head that lands on aconductor pipe and connects to surface casing. The head's upper end hasan external threaded connection to which various components can beconnected depending on the desired arrangement. For example, a rotatableflange or other connector can thread onto the head's upper end, and acomponent of a blow-out preventer (BOP) can bolt to the rotatable flangeabove the casing head.

The assembly also includes a casing hanger that lands in the casing headto support production casing within the surface casing. When installedin the head, the hanger's upper end extends beyond the head's top edge.This exposed end has an external threaded connection that allows variouscomponents to connect to the hanger's upper end depending on the desiredarrangement. For example, a locking ring can threadably connect to thehead's external threaded connection to support the casing hanger in thecasing head. Then, a rotatable flange or other connector can threadablyconnect to the hanger's exposed end so that a completion spool, gatevalve, or other wellhead component can bolt to the rotatable flangeabove the casing hanger.

In other arrangements, the casing head can be used with conventionalwellhead components and can be landed through a riser using a runningtool threaded to internal threads in the casing head. In addition, thecasing hanger used in the various arrangements can be fluted, and apack-off assembly that allows testing of inner and outer seals can beused with the fluted casing hanger. In still other arrangements, modularhead components of the assembly permit operators to make variousarrangements of the head components to suit their needs in eithersingle-bowl or multiple-bowl arrangements and to facilitate contingencyoperations in the event a stuck pipe occurs.

Turning now to the drawings, FIG. 2 illustrates a well completionassembly having a casing head 100 and a casing hanger 200. The casinghead 100 with a landing ring 22 attached thereto lands on a support ring20 on an exposed end of conductor pipe 10, and an internal threadedconnection 104 connects to surface casing 12. Side ports 102 for valvesor the like are provided in the head's bore 101 for various uses duringwell operations. When the casing head 100 is installed as shown, flutes(not shown) in the rings 20/22 can allow cement to be inserted betweenthe conductor pipe 10 and the surface casing 12 during a cementing job.

In the arrangement, a rotatable flange 110 threadably connects to anexternal threaded connection 106 on the casing head's upper end, and aBOP stack component 50 nipples up to the casing head 100 by bolting tothe flange 110. To seal this connection, a gasket is disposed in agroove at head's top edge. Rather than using the rotatable flange 110 asshown, a drilling adapter, such as element 530 shown in FIG. 10A, orother connector could alternatively be used.

Also in the arrangement, the casing hanger 200 has production casing 14connected by an internal threaded connection 204 at the hanger's lowerend. To install the hanger 200 and the casing 14, a running tool 52connects by a coupling 54 to an external threaded connection 206 at thehanger's upper end, and the hanger 200 and the casing 14 are run throughthe BOP stack component 50 and into the casing head 100. Once run in,the casing hanger 200 lands in the head 10 by engaging an internalshoulder 103 so that the production casing 14 is supported within thesurface casing 12.

As will be appreciated, each of the components of the assembly iscomposed of a suitable material known in the art for a wellheadcomponent. Preferably, the threaded connections (106, 204, and 206) haveACME-2G left-handed thread forms. For some exemplary dimensions, theconductor pipe 10 may be 16-in. casing, and the surface and productioncasings 12/14 may respectively be 9⅝-in. and 4½-in. casings. Theconnection of the rotatable flange 110 to the BOP stack component 50 maybe 11-in. rated at a working pressure of 5,000-PSI. As one skilled inthe art will appreciate, these values are provided as examples forillustrative purposes, and components of the assembly can be sized for13-inch connections and other sizes of casing.

During operations, it would be desirable to be able to nipple up atubing spool above a production casing hanger without requiring the useof secondary pack-off to seal around the hanger. As shown in FIG. 3A,the disclosed assembly allows a completion spool 60 to nipple up to thecasing hanger 200 of the disclosed assembly without the need forsecondary pack-off. In this arrangement, a locking ring 120 defining acentral opening 122 installs over the hanger's end exposed above thehead 100, and internal threads on the ring's sides 126 couple to theexternal threaded connection 106 on the casing head 100. This connection106 can be 11-in. rated at a working pressure of 10,000-PSI. As shown inthe detail of FIG. 3B, the ring's inside surface 124 engages thehanger's upper shoulder 207 to hold the hanger 100 in the head 100.Also, the inside surface 122 engages a gasket 108 disposed in a grooveat the head's top edge.

With the ring 120 installed, the tubing spool 60 can couple directly tothe exposed end of the hanger 200. In particular, a rotatable flange 62or other connector threads onto the hanger's external threadedconnection 206, and the spool 60 bolts to the rotatable flange 62. Agasket is disposed in a groove at the hanger's top edge to seal theconnection. This connection between hanger 200 and spool 60 can be 41/16-in. rated at a working pressure of 10,000-PSI, for example. Withthe spool 60 connected, other components can then be connected above thespool 60, and tubing (not shown) can eventually be hung in the spool'sbowl using a tubing hanger (not shown). Because the completion spool 60nipples up directly to the hanger 200, the casing hanger 200 essentiallyacts as a spool, and the need for secondary pack-off is eliminated.

As shown in detail in FIG. 3B, the hanger's upper shoulder 207 defines atest port 208 that communicates between two sealing seats 209 disposedabout the hanger's outer cylindrical surface. With the hanger 200installed in the head's internal bore 101 as shown, this test port 208is accessible through the ring's opening 122 so that the seal formedbetween the sealing seats 209 and the casing head's internal bore 101can be tested.

FIG. 4 shows a similar arrangement with a gate valve 65 nipple up to thecasing hanger 200 of the assembly. Again, the rotatable flange 62couples to the external threaded connection 206 on the exposed end ofthe hanger 200, and the gate valve 65 bolts to the flange 62. As will beappreciated, the gate valve 65 may be used for fracing operations or thelike. With respect to frac operations, it would be desirable to be ableto frac at high pressures without needing to use an isolation tool inthe wellhead. In current arrangement of the disclosed assembly, there isno need to use an isolation tool (or a nipple up/down apparatus for suchan operation). Rather, interior frac pressures can reach as high as theinternal yield pressure of the production casing 14 itself because thehousing of the casing 14 communicates directly with the gate valve 65through the casing hanger 200. Therefore, frac pressures that can beused with the disclosed assembly are not limited by conventional flangepressure ratings of adapters or the like that would typically be usedabove a production casing hanger.

The hanger 200 shown in FIG. 4 has flutes that allow fluid returns pastthe hanger 200 when used in some arrangements. In FIG. 4, however, apack-off assembly 210 having a pack-off plate and other components formsa seal between the fluted hanger 200 and the inside surface of lockingring 120. When this form of pack-off is done, it is desirable to have anadequate and convenient way to test the pack-off's inner and outerseals. In the prior art, however, the only way to test the integrity ofa pack-off's seals requires operators to nipple up the next spool abovethe pack-off assembly and to then perform a flange pressure test. Forexample, FIG. 9A discussed below shows a conventional pack-off plate 74having an inner seal that engages casing 14 and having an outer sealthat engages casing head 100. To test the seals, a tubing spool 70 mustbe nippled up to the casing head 100, and a flange pressure test must beperformed using a test port 73 on the spool 70. If the test fails,operators have to nipple down the spool 70 and pull out the pack-offplate 74 to investigate the cause. This procedure can be time intensive.

In contrast, the pack-off assembly 210 in FIG. 4 has a top-access testport 212 accessible through the sealing ring's opening 122. This testport 212 communicates between two sets of inner and outer seals on theassembly 210. In this way, the sealing integrity of the assembly's innerand outer seals can be tested simultaneously and as soon as the assembly210 is installed so that time can be saved on site. Further details of afluted hanger and a pack-off assembly are discussed below with referenceto FIGS. 5A through 8C.

FIGS. 5A-5B illustrate a fluted casing hanger 300 for use with thedisclosed assembly in top and cross-sectional views, respectively. Aswith other hangers disclosed herein, the fluted hanger 300 has aninternal bore 302 with an internal threaded connection 303 at its lowerend to connect to production casing (not shown). In addition, thehanger's upper end has an external threaded connection 306 for couplingto running tool as in FIG. 2 or to a rotatable flange as in FIG. 3A.Furthermore, the hanger's top edge defines an annular well 308 for agasket (not shown) used to seal engagement between the hanger 300 andthe various other components discussed herein.

Being fluted, however, the hanger's lower end defines a plurality offlutes or cutaways 304 (four shown in FIG. 5A) that enable fluid returnsto communicate past the hanger 300. In another distinction, the hanger300 as shown in FIG. 5B has a blunt or flat lower end as opposed to thesubstantially extended and narrowed lower end of the other hangersdisclosed herein. It will be appreciated that any of the other hangers(either fluted or not) disclosed herein may have a similar blunt end ifdesired.

As briefly discussed above in FIG. 4, a pack-off assembly 210 can beused to seal communication through flutes of a fluted hanger whenreturns are no longer desired. When used, the pack-off assembly 210preferably allows the sealing integrity of inner and outer seals to betested in an adequate and convenient way. For such as a pack-offassembly, FIG. 6 illustrates a pack-off plate or sealing ring 400capable of such testing ability, and FIGS. 7A-7B illustrate the pack-offplate 400 and an additional sealing ring 430 positioned on the flutedcasing hanger 300 of FIGS. 5A-5B.

As best shown in FIGS. 7A-7B, the sealing ring 430 positions adjacent alowermost shoulder 309 a on the hanger 300. The pack-off plate 400(shown in cross-section in FIG. 6) has a central opening 402 andpositions over the hanger's narrower end and threads its internalthreads 407 onto intermediate threaded connection 307 on the hanger 300.This pack-off plate 400 may be referred to as a production casing hangerpack-off or an H-plate.

As the pack-off plate 400 is tightened onto the hanger 300, internalseals 450 (e.g., O-rings) on the pack-off plate 400 eventually engage aside portion 309 c of the hanger's surface, while outer seals 440 (e.g.,O-rings) engage the internal wall of the casing head's bore (not shown).Likewise, the plate's lower lip 404 wedges in between the lowermost ring430 and a side portion 309 b of the hanger's surface so that thelowermost ring 430 seals against the internal wall of the casing head'sbore (not shown).

To test the sealing integrity, the pack-off plate 400 defines a testport 406 in its top surface 405 that is accessible when the locking ring(e.g., 120 in FIG. 4) is used. As best shown in the cross-section of theplate 400 in FIG. 6, the test port 406 communicates with spaces betweenthe outer and inner seats 408/409 for the seals (440/450) so that theirsealing integrity can be tested. Because this test port 406 isaccessible through the locking ring's opening (122), this testing can bedone during partial assembly of the pack-off or after complete assemblyof the arrangement.

In addition to being used with the casing hanger 200, pack-off assembly210, and other components discussed above, the casing head 100 can beused on its own with various other wellhead components in a number ofother arrangements. In one example shown in FIG. 8, the casing head 100can be run through a riser 16 and landed on a support ring 20 using aninternal running tool 18. To run the head 100, the internal running tool18 has a coupling 19 that attaches to an internal threaded connection107 in the casing head's bore 101.

In other uses, the casing head 100 can also be used on its own inconjunction with some conventional wellhead components. For example,FIG. 9A shows the casing head 110 having a completion spool 70 nippledup to the head 100 with a rotatable flange 110. FIG. 9B shows a similararrangement, but in this example, a completion spool 80 and adapter 82nipple up to the casing head 100 with a rotatable flange 110.

In both arrangements, a conventional hanger 76 having slips 77 lands onthe head's internal shoulder 103 to support the production casing 14,and a conventional pack-off plate 74 seals against the production casing14 and the head 100. Segmented rings 72 engage against the productioncasing 14 within the spool 70 in FIG. 9A, while internal seals in theadapter 82 engage against the end of production casing 14 in FIG. 9B.

The casing head 100 disclosed above represents a single-bowl type,meaning that it defines a single bowl and has a length for supporting asingle hanger. FIGS. 10A-10B illustrates a wellhead completion assemblyhaving a casing head 500 that represents a double-bowl type.Accordingly, one casing hanger 510 (FIG. 10A) or two casing hangers510/540 (FIG. 10B) can be used with this casing head 500. Although shownas fluted, the casing hangers 510/540 could be mandrel hangers, ifdesired.

In the arrangement of FIG. 10A, a BOP stack component 50 nipples up tothe casing head 500. In this example, the connection uses a drillingadapter 530 that has a locking assembly 532 for quick connect to thecasing head 500, pack-off screws 534 for other purposes, and a flange536 for bolting to the BOP stack component 50. The casing hanger 510lands in the casing head 500 through the BOP stack component 50 using arunning tool (not shown). A pack off assembly 520 having pack-offelements 522 installs above the casing hanger 510, and pack-off screws524 on the head 500 engage the elements 522. Once installed, thepack-off assembly 520 forms an additional bowl in the head 500. In thisexample, the conductor pipe 10 can be 20-in. casing, and the surfacecasing 12 can be 9⅝-in casing. The casing hanger 510 can support 7-in.production casing.

In the arrangement of FIG. 10B, the casing hanger 510 and the pack-offassembly 520 again install in the casing head 500, and a fluted hanger540 and pack off assembly 545 install in the end of the casing head 500.A locking ring 550 threads onto the end of the casing head 500 andengages the pack-off assembly 545, and a completion spool 560, gatevalve, or other component nipples up to the end of the fluted hanger 540with a rotatable flange 562 or other connector. In this example, thefirst hanger 510 can support 7-in. production casing 14, while thesecond hanger 540 can support 4.5-in. casing 15.

In addition to these arrangements of FIGS. 10A-10B, the double-bowl typecasing head 500 can be landed through a 20-in. riser using a runningtool in much the same manner as depicted in the example of FIG. 8, withthe exception that the running tool couples to the outer threadedconnection at the top end of the casing head 500. Moreover, the casinghead 500 and other components of FIGS. 10A-10B can be used withcompletion spools, adapters, and other conventional components similarto the arrangements in FIGS. 9A-9B (e.g., elements 70, 72, 74, 76, 77,80, and 82).

The double-bowl type casing head as shown in FIGS. 10A-10B can be usedin various operations when several casing strings are to be rundownhole. FIGS. 11A-11E illustrate another wellhead completion assembly600 in various stages of assembly that can support several casingstrings. In addition, to being able to support multiple strings, thisassembly 600 has modular head components 610 and 620 that offer a numberof advantages, including allowing the assembly 600 to be assembled indifferent arrangements and facilitating contingency operations when astuck pipe occurs before a hanger can be properly landed in the head.

As shown in FIG. 11A, the modular assembly 600 includes first and secondhead components 610 and 620. The first head component 610 can be similarto the casing head of previous embodiments, such as casing head 100 inFIG. 2, and can be used alone in a single bowl type of arrangement.Alternatively, the second head component 620 can connect to the firsthead component to make a double-bowl type of casing head.

In assembling the double bowl arrangement, for example, the first headcomponent 610 connected to outer casing 12 lands on the landing assembly20, and the second head component 620 supported by running tool 54threads to the first component 610 at a threaded connection 630. Thisthreaded connection 630 can use the same type of threading and rating asprevious embodiments. For example, this connection 630 can be similar tothe connection 106 in FIG. 2 having ACME-2G left-handed thread form andcan be 11-in. rated at a working pressure of 10,000-PSI. Holes 632 andsetscrews (not shown) may also be used to couple the second component620 to the first component 610.

As shown in FIG. 11B, another running tool 54 runs a hanger 650 andattached inner casing 14 through the head components 610/620 and landsthe hanger 650 on the shoulder 612 inside the first component 610.Subsequently, as shown in FIG. 11C, another running tool 56 lands apack-off plate 660 above the hanger 650. The modular assembly 600'sresulting double-bowl type of arrangement is shown in FIG. 11D. At thispoint in the assembly and as shown in FIG. 11E, additional pack-offcomponents, another inner casing, and an additional hanger can be landedin the second head component 620 as with the assembly in FIGS. 10A-10B.In this way, the modular assembly 600 can support multiple casingstrings. For example, an 11-inch embodiment of the assembly 600 couldsupport two casing strings, while a 13-inch embodiment of the assembly600 could support three casing strings.

As shown in FIGS. 11A-11E, the first and second head components 610/620of the modular assembly 600 can be used to create a double-bowl type ofcasing head. Because the disclosed assembly 600 is modular, the firsthead component 610 can be used by itself. As shown in FIGS. 12A-12B, forexample, the first head component 610 can be landed on the landingassembly 20 with a running tool 54, and a quick connect drilling adapter530 or some other desired component can be attached to the firstcomponent 610 to complete the assembly. Alternatively, the first headcomponent 610 can be used in other arrangements disclosed herein, suchas in FIGS. 2, 3A, 4, and 9A-9B. In another alternative shown in FIG.13, two of the second head components 620 a-b can be stacked on top ofone another above the first head component 610 to create a threecomponent modular assembly, which can be used to support multiple casingstrings.

Not only does the modular assembly 600 provide for versatilearrangements, but it facilitates contingency operations when a stuckpipe occurs. When running the casing 14 and hanger 650 through the headcomponents 610/620 and the outer casing 12, for example, the innercasing 14 may become stuck in what is commonly referred to as a stuckpipe situation—an example of which is shown in FIG. 14A. Because theinner casing 14 cannot be inserted enough to allow the attached hanger650 to be landed on the shoulder 612, operators must perform acontingency operation that involves using slips to secure the innercasing 14 in tension within the casing head and cutting the excessportion from the inner casing 14 that has been prevented from passingthrough the casing head.

In a conventional double-bowl casing head, cutting the excess casing canbe difficult because the point at which the cut must be made lies deepwithin the double-bowl casing head. In other words, an operator has tocarefully cut the casing within the confined space of the double-bowlhead with a welding tool and then to prepare the end of the cut casingproperly for further operations.

The modular assembly 600, however, facilitates stuck pipe contingencyoperations. When a stuck pipe occurs as in FIG. 14A, operators positiona slip assembly 670 and pack-off 672 in the first component 610 as shownin FIG. 14B and then remove the second component 620 from the firstcomponent 610 at the threaded connection 630. Removing the secondcomponent 620 leaves the excess casing 14 exposed above the firstcomponent 610. Operators can then more readily cut the excess casing 14at the appropriate point, level the cut end 15, and create the neededchamfer at the edge. After these steps have been completed, operatorscan reconnect the second component 620 to the first component 610.Alternatively, operators can attach a rotating flange 674 to theconnection end 631 of the first component 610 as shown in FIG. 14C orcouple components of some other desired arrangement to the firstcomponent 610.

In addition to facilitating preparation of the inner casing 14 duringstuck pipe contingency operations, the modular assembly 600 also helpsoperators perform modifications to a control line when a stuck pipeoccurs. For example, FIG. 15A shows the modular assembly 600 having acontrol line 700 that runs down the annulus to a valve or the like (notshown). The control line 700 connects by a ferrule coupling 702 to ahanger 650, and a side coupling 704 in the first head component 610communicates with a port in the hanger 650 to communicate with thecontrol line 700.

If a stuck pipe occurs while running the inner casing 14, the hanger650, and the control line 700 downhole, operators have to modify thearrangement of the control line 700 to connect it to the side coupling704. In a conventional double-bowl type of head, operators would have tomodify the control line's connection by making modifications deep withinthe double-bowl head and confined in the annulus between the innercasing and the head.

The disclosed modular assembly 600, however, alleviates some of thisdifficulty. For example, as shown in FIG. 15B, the second component 620can be removed from the first head component 610 giving operators easieraccess to the control line 700 and the inside of the coupling 704.Before putting the slip assembly 670 and pack-off 672 in the head, forexample, operators can wind excess amounts of control line 700 in wraps705 around the casing 14 and attach the line 700 to the coupling 704inside the first component 610 while having easier access inside theannulus. After setting up the control line 700, putting the slipassembly 670 and pack-off 672 in the first head component 610, andcutting the excess of the casing 14, operators can reconnect the secondcomponent 620 to the first component 610. Alternatively, operators canattach a rotating flange 674 to the end of the first component 610 asshown in FIG. 15C, or couple components of some other desiredarrangement to the first component 610.

The foregoing description of preferred and other embodiments is notintended to limit or restrict the scope or applicability of theinventive concepts conceived of by the Applicants. For example, it willbe appreciated with the benefit of the present disclosure thatcomponents of one embodiment of the wellhead completion assembly can becombined with components of another embodiment to produce a variety ofversatile arrangements for well completions. In exchange for disclosingthe inventive concepts contained herein, the Applicants desire allpatent rights afforded by the appended claims. Therefore, it is intendedthat the appended claims include all modifications and alterations tothe full extent that they come within the scope of the following claimsor the equivalents thereof.

What is claimed is:
 1. A wellhead assembly, comprising: a casing headconnecting to casing at a wellhead, the casing head having an internalsurface and having a first connection disposed on the casing head; acasing hanger disposing in the casing head, the casing hanger having anexternal surface and having a distal end, the distal end extendingbeyond the casing head and having a second connection disposed on thedistal end, the second connection for connecting at least one componentabove the casing hanger; a pack-off plate disposing about the casinghanger and having an inner surface, an outer surface, and an uppersurface, the upper surface defining a test port, the inner surfacesealably engaging the external surface of the casing hanger, the outersurface sealably engaging the internal surface of the casing head; and ahead ring connecting to the first connection of the casing head, thehead ring engaging the upper surface of the pack-off plate and definingan opening through which the distal end of the casing hanger extends,wherein the test port is accessible through the opening in the head ringand communicates with the sealed engagement between the inner andexternal surfaces or between the outer and internal surfaces.
 2. Theassembly of claim 1, wherein the first connection comprises a firstthread disposed about an external surface of the casing head, andwherein the second connection comprises a second thread disposed aboutthe external surface on the distal end of the casing hanger.
 3. Theassembly of claim 1, wherein the pack-off plate comprises: a pair ofseals disposed on the inner surface and engaging the external surface ofthe casing hanger; wherein the test port defined in the upper surfaceand accessible through the opening in the head ring communicates betweenthe pair of seals on the pack-off plate.
 4. The assembly of claim 1,wherein the pack-off plate comprises: a pair of seals disposed on theouter surface and engaging the internal surface of the casing head;wherein the test port defined in the upper surface and accessiblethrough the opening in the head ring communicates with the pair of sealson the pack-off plate.
 5. The assembly of claim 1, wherein the casinghead comprises a single-bowl arrangement defining an internal shoulderwithin an internal bore, the casing hanger supported by the internalshoulder.
 6. The assembly of claim 1, wherein the casing head comprisesa double-bowl arrangement defining an internal shoulder within aninternal bore, the casing hanger disposing on one or more componentssupported by the internal shoulder.
 7. The assembly of claim 1, whereinthe casing hanger defines a shoulder, wherein the head ring defines asurface adjacent the opening, and wherein the pack-off plate engagesbetween the shoulder and the surface.
 8. The assembly of claim 1,wherein the casing hanger defines at least one flute, and wherein thepack-off plate seals fluid communication through the at least one flute.9. The assembly of claim 1, wherein the casing hanger defines anexternal thread disposed thereabout, and wherein the pack-off platethreadably connects on the external thread.
 10. The assembly of claim 1,further comprising a sealing ring disposing about the external surfaceof the casing hanger, wherein the pack-off plate comprises a lip wedgingbetween the sealing ring and the external surface of the casing hanger.11. A wellhead assembly, comprising: a first casing head connecting atone end to casing at a wellhead and defining a first shoulder therein,the first casing head having a first external threaded connection atanother end; one or more second casing heads each having a firstinternal threaded connection at one end and each having a secondexternal threaded connection at another end; a casing hanger disposingin the assembly and having a distal end with a fourth connection forconnecting to at least one component above the casing hanger; and a headring connecting to the assembly and defining an opening through whichthe distal end of the casing hanger extends, wherein in a single-bowlarrangement, the first casing head connects independently to the casingat the wellhead, the casing hanger disposes in the first casing head,and the head ring connects to the first external threaded connection ofthe first casing head and has the distal end of the casing hangerextending through the opening; and wherein in one or more multiple-bowlarrangements, the first casing head connects to the casing, and thefirst internal threaded connection of at least one of the one or moresecond casing heads threads onto the first external threaded connectionof the first casing head.
 12. The assembly of claim 11, wherein thefirst internal threaded connection on each of the one or more secondcasing heads is configured to thread onto the first external threadedconnection of the first casing head and is configured to thread onto thesecond external threaded connections of the one or more second casingheads.
 13. The assembly of claim 11, wherein in the single-bowlarrangement, the casing hanger is supported by the first shoulder in thefirst casing head and has the distal end extending beyond the endthereof.
 14. The assembly of claim 11, wherein in the one or moremultiple-bowl arrangements, the casing hanger disposes in an uppermostof the one or more second casing heads, and the head ring threads ontothe second external threaded connection of the uppermost of the one ormore second casing heads and has the distal end of the casing hangerextending through the opening.
 15. The assembly of claim 14, wherein inthe one or more multiple-bowl arrangements, the assembly furthercomprises one or more pack-off components supported by the firstshoulder in the first casing head, the casing hanger being supported bythe one or more pack-off components and having the distal end extendingbeyond the uppermost of the one or more second casing heads.
 16. Theassembly of claim 11, wherein a portion of the head ring directlyengages a second shoulder of the casing hanger, and wherein the casinghanger comprises: a pair of seals on an outer surface for engaging acasing head sidewall, and a test port defined in the second shoulder andaccessible through the opening in the head ring, the test portcommunicating between the pair of seals.
 17. The assembly of claim 11,further comprising a pack-off plate disposing between the casing hangerand the head ring, the pack-off plate having an inner portion sealingagainst the casing hanger, the pack-off plate having an outer portionsealing against a casing head sidewall.
 18. The assembly of claim 17,wherein the pack-off plate comprises: a pair of first seals on the outerportion; a pair of second seals on the inner portion; and a test portdefined in an upper surface and accessible through the opening in thehead ring, the test port communicating with the inner and outer portionsbetween the first and second seals.
 19. A wellhead assembly, comprising:a first casing head connecting at one end to casing at a wellhead anddefining a first shoulder therein, the first casing head having a firstconnection at another end; and one or more second casing heads eachhaving a second connection at one end and each having a third connectionat another end; a casing hanger disposing in the assembly and having adistal end with a fourth connection for connecting to at least onecomponent above the casing hanger; and a head ring connecting to theassembly and defining an opening through which the distal end of thecasing hanger extends, wherein in a single-bowl arrangement, the firstcasing head connects independently to the casing at the wellhead withoutthe one or more second casing heads, whereby the casing hanger disposesin the first casing head, and whereby the head ring connects to thefirst connection of the first casing head and has the distal end of thecasing hanger extending through the opening, and wherein in one or moremultiple-bowl arrangements, the first casing head connects to thecasing, and the second connection of at least one of the one or moresecond casing heads connects to the first connection of the first casinghead, whereby the casing hanger disposes in an uppermost of the one ormore second casing heads, and whereby the head ring connects to thethird connection of the uppermost of the one or more second casing headsand has the distal end of the casing hanger extending through theopening.
 20. The assembly of claim 19, wherein in the single-bowlarrangement, the casing hanger is supported by the first shoulder in thefirst casing head and has the distal end extending beyond the endthereof.
 21. The assembly of claim 19, wherein in the one or moremultiple-bowl arrangements, the assembly further comprises one or morepack-off components supported by the first shoulder in the first casinghead, the casing hanger being supported by the one or more pack-offcomponents and having the distal end extending beyond the uppermost ofthe one or more second casing heads.
 22. The assembly of claim 19,wherein a portion of the head ring directly engages a second shoulder ofthe casing hanger, and wherein the casing hanger comprises: a pair ofseals on an outer surface for engaging a casing head sidewall, and atest port defined in the second shoulder and accessible through theopening in the head ring, the test port communicating between the pairof seals.
 23. The assembly of claim 19, further comprising a pack-offplate disposing between the casing hanger and the head ring, thepack-off plate having an inner portion sealing against the casinghanger, the pack-off plate having an outer portion sealing against acasing head sidewall.
 24. The assembly of claim 23, wherein the pack-offplate comprises: a pair of first seals on the outer portion; a pair ofsecond seals on the inner portion; and a test port defined in an uppersurface and accessible through the opening in the head ring, the testport communicating with the inner and outer portions between the firstand second seals.
 25. The assembly of claim 19, wherein the secondconnection on each of the one or more second casing heads is configuredto connect to the first connection of the first casing head and isconfigured to connect to the third connections of the one or more secondcasing heads.
 26. A wellhead assembly method, comprising: disposing acasing hanger in a casing head at a wellhead with a first end of thecasing hanger extending beyond a second end of the casing head;disposing a pack-off plate on the first end of the casing hanger;sealing the pack-off plate between the casing hanger and the casing headby sealably engaging an inner surface of the pack-off plate with anexternal surface of the casing hanger and by sealably engaging an outersurface of the pack-off plate with an internal surface of the casinghead; disposing the first end of the casing hanger through an opening ina head ring; connecting the head ring on the second end of the casinghead with the first end of the casing hanger extending through theopening of the head ring; and leaving a test port in an upper surface ofthe pack-off plate accessible through the opening in the head ring, thetest port communicating with the sealed engagement between the inner andexternal surfaces or between the outer and internal surfaces.
 27. Themethod of claim 26, comprising initially connecting the casing head tosurface casing.
 28. The method of claim 26, wherein disposing thepack-off plate on the first end of the casing hanger comprises threadingthe pack-off plate on an external thread of the casing hanger.
 29. Themethod of claim 26, wherein disposing the pack-off plate on the firstend of the casing hanger comprises sealing an inner pair of seals on theinner surface of the pack-off plate against the external surface of thecasing hanger and sealing an outer pair of seals on the outer surface ofthe pack-off plate against the internal surface of the casing head. 30.The method of claim 29, further comprising testing the inner and outerpairs of seals via the test port defined in the upper surface of thepack-off plate and accessible through the opening in the head ring. 31.The method of claim 26, wherein disposing the pack-off plate on thefirst end of the casing hanger comprises: wedging a lip on the pack-offplate between a hanger ring and the external surface of the casinghanger, and engaging the hanger ring against the internal surface of thecasing head.
 32. The method of claim 26, further comprising connectingan additional component above the first end of the casing hanger. 33.The method of claim 32, wherein connecting an additional component abovethe first end of the casing hanger comprises disposing a connector tothe first end of the casing hanger; and connecting the additionalcomponent with the connector.
 34. A wellhead assembly, comprising: acasing head connecting to casing at a wellhead and having at least twohead components interconnecting end-to-end to extend one from another, afirst of the at least two head components having an internal shouldertherein, a second of the at least two head components having a firstexternal connection disposed thereon; a casing hanger disposing in thecasing head and having a distal end, the distal end extending beyond thesecond of the at least two head components and having a second externalconnection disposed thereon, the second external connection forconnecting at least one component above the casing hanger; a pack-offplate disposing about the casing hanger and sealably engaging betweenthe casing hanger and the casing head; and a head ring connecting to thefirst external connection of the second of the at least two headcomponents, the head ring engaging the pack-off plate and defining anopening through which the distal end of the casing hanger extends. 35.The assembly of claim 34, wherein the first external connectioncomprises a first thread disposed about an external surface of thesecond of the at least two head components, and wherein the secondexternal connection comprises a second thread disposed about an externalsurface on the distal end of the casing hanger.
 36. The assembly ofclaim 34, wherein the pack-off plate comprises: a pair of seals disposedon an inner portion and engaging an external surface of the casinghanger; and a test port defined in an upper surface and accessiblethrough the opening in the head ring, the test port communicatingbetween the pair of seals on the pack-off plate.
 37. The assembly ofclaim 34, wherein the pack-off plate comprises: a pair of seals disposedon an outer portion and engaging an internal surface of the casing head;and a test port defined in an upper surface and accessible through theopening in the head ring, the test port communicating with the pair ofseals on the pack-off plate.
 38. The assembly of claim 34, wherein thecasing head is supported by the internal shoulder.
 39. The assembly ofclaim 38, wherein one or more components disposed in the casing headsupport the casing hanger on the internal shoulder.
 40. The assembly ofclaim 34, wherein the first of the at least two head components connectsto the casing and has a second external connection disposed thereon, andwherein the second of the at least two head components has an internalconnection disposed at one end and has the first external connectiondisposed at another end, the internal connection connecting to thesecond external connection on the first of the at least two headcomponents.
 41. The assembly of claim 34, wherein the casing hangerdefines a shoulder, wherein the head ring defines a surface adjacent theopening, and wherein the pack-off plate engages between the shoulder andthe surface.
 42. The assembly of claim 34, wherein the casing hangerdefines at least one flute, and wherein the pack-off plate seals fluidcommunication through the at least one flute.
 43. The assembly of claim34, wherein the casing hanger defines an external thread disposedthereabout, and wherein the pack-off plate threadably connects on theexternal thread.
 44. The assembly of claim 34, further comprising asealing ring disposing about an external surface of the casing hanger,wherein the pack-off plate comprises a lip wedging between the sealingring and the external surface of the casing hanger.
 45. A wellheadassembly, comprising: a first casing head connecting at one end tocasing at a wellhead and defining a first shoulder therein, the firstcasing head having a first external threaded connection at another end;one or more second casing heads each having a first internal threadedconnection at one end and each having a second external threadedconnection at another end; a casing hanger disposing in the assembly andhaving a distal end with a fourth connection for connecting to at leastone component above the casing hanger; and a head ring connecting to theassembly and defining an opening through which the distal end of thecasing hanger extends, wherein in a single-bowl arrangement, the firstcasing head connects independently to the casing at the wellhead; andwherein in the one or more multiple-bowl arrangements, the first casinghead connects to the casing, the first internal threaded connection ofat least one of the one or more second casing heads threads onto thefirst external threaded connection of the first casing head, the casinghanger disposes in an uppermost of the one or more second casing heads,and the head ring connects to the second external threaded connection ofthe uppermost of the one or more second casing heads and has the distalend of the casing hanger extending through the opening.
 46. The assemblyof claim 45, wherein the first internal threaded connection on each ofthe one or more second casing heads is configured to thread onto thefirst external threaded connection of the first casing head and isconfigured to thread onto the second external threaded connections ofthe one or more second casing heads.
 47. The assembly of claim 45,wherein in the single-bowl arrangement, the casing hanger is supportedby the first shoulder in the first casing head and has the distal endextending beyond the end thereof.
 48. The assembly of claim 45, whereina portion of the head ring directly engages a second shoulder of thecasing hanger, and wherein the casing hanger comprises: a pair of sealson an outer surface for engaging a casing head sidewall, and a test portdefined in the second shoulder and accessible through the opening in thehead ring, the test port communicating between the pair of seals. 49.The assembly of claim 45, further comprising a pack-off plate disposingbetween the casing hanger and the head ring, the pack-off plate havingan inner portion sealing against the casing hanger, the pack-off platehaving an outer portion sealing against a casing head sidewall.
 50. Theassembly of claim 49, wherein the pack-off plate comprises: a pair offirst seals on the outer portion; a pair of second seals on the innerportion; and a test port defined in an upper surface and accessiblethrough the opening in the head ring, the test port communicating withthe inner and outer portions between the first and second seals.